class Circle {
  constructor(radius) {
    this.radius = radius;
  }
  //圆直径
  get diameter() {
    return this.radius * 2
  }
  //圆面积
  get area() {
    return Math.PI * this.radius * this.radius
  }
  //圆周长
  get circumference() {
    return 2 * this.radius * this.radius
  }
}

module.exports = Circle

console.log(module);
